To prevent unauthorized access to a vehicle, in particular a car, modern access authorization systems or access systems in vehicles use electronic security systems, wherein, to authenticate a user, data communication is made between a first communication device of the vehicle and a second communication device in a mobile ID transmitter of the user, such as a key or key fob. To this end, initially request signals having a specific field strength are emitted at regular intervals by the first communication device of the vehicle, in order to check whether there is a mobile ID transmitter in a proximity area around the vehicle. If a mobile ID transmitter approaches the vehicle and can then receive the request signals of said vehicle, then it will respond to the reception of a request signal in order to initiate an authentication procedure or a pre-authentication procedure. Thereby there is an exchange of data telegrams in which finally the mobile ID transmitter transmits its authentication code to the vehicle. When the checking of the authentication code is successful, it is then possible for a user who is directly beside the vehicle to trigger the unlocking of a corresponding vehicle door or all vehicle doors by operating a door handle. Usually, after the door handle has been operated, another authentication is carried out between the vehicle and the ID transmitter, whereby the at least one door of the vehicle is only unlocked after the second authentication has been successfully performed. As in this case a user does not have to actively operate a mechanical or electronic key, this kind of access authorization is also called passive access authorization check, and the corresponding access authorization systems are called passive electronic access authorization systems.
Disadvantageous in a method of this kind for attaining access to a vehicle has proved to be that a user who is at the vehicle has first to operate a door handle to achieve access into the vehicle and further must await the additional authentication. This can be particularly awkward if a user has just returned to the vehicle after shopping and is laden with shopping.